1. Field of the Invention
This invention relates to a passive seat belt system for automatically applying or releasing a webbing when a passenger gets on or gets off an automotive vehicle, and more specifically to a means for allowing or preventing the operation of the emergency locking retractor (ELR) of such a passive seat belt system under predetermined specific conditions. 2. Description of the Prior Art
The ELR of a passive seat belt system of the above kind is accompanied by an inconvenience that if it is actuated while not needed, for example, while its anchor is moving or when the associated passenger seat is slid for its positional adjustment, any further release of the webbing is locked and the anchor cannot be moved even when a passenger tries to move the anchor for making the webbing loose.
It may hence be contemplated to eliminate the above-described inconvenience by releasing the blocking of the ELR only when the outboard end of the webbing is at the applied end.
FIGS. 1 and 2 illustrate by way of example conventional control circuits for such an ELR. The former control circuit is applied to a passive seat belt system of a type such that an anchor is caused to move by a motor. When an associated webbing is not at the applied end, a rear switch 12 is closed to turn on a solenoid 30 which serves to control the locking of an associated ELR as will be described subsequently. As a result, the ELR is preventing from locking the webbing. The latter control circuit is applied to a passive seat belt system of a type such that an anchor does not move. An associated ELR is prevented from locking an associated webbing only when an associated door switch or latch switch 11 is closed.
In the case of a type that the blocking of an ELR is controlled as mentioned above responsive to the switch 12 which indicates the presence of a webbing at a retreated end, there is a potential problem that the ELR could no longer be controlled if the switch 12 fails. In the case of another type that the blocking of an ELR is controlled by using one or more mechanical elements, there is also a high chance that the operation of the ELR could be hampered by friction and breakdown of the transmitting part.
Conventional passive seat belt systems, including the above-exemplified systems, have not been able to get rid of other inconvenience, for example, that an ELR is actuated upon movement of a passenger seat when the ELR is mounted on the passenger seat.